The invention relates to apparatus for controlling valves in linear displacement along respective axes, the apparatus comprising as many actuators as there are valves, each actuator having an armature of ferromagnetic material secured to a valve-pusher rod and at least one return spring having one end bearing against the rod and having its opposite end bearing against stationary anchor means that are adjustable in position relative to a case of the actuator containing electromagnets for moving the armature in linear manner, adjustment of the anchor means enabling an armature rest position to be set.
Actuators of this kind can have two opposing return springs (U.S. Pat. No. 4,614,170) or a single spring working alternately in traction and in compression (French Appln No. 98/11670). They can have a single coil (U.S. patent application Ser. No. 09/806,711 corresponding to French Appln No. 98/12489 or French Appln No. 99/04472) or two coils.
The invention seeks in particular to provide valve control apparatus in which the adjustment means are compact and make it possible, once the apparatus has been mounted on the cylinder head of an engine, to make adjustments in a very short length of time.
To this end, the invention provides apparatus wherein the anchor means comprise a toothed wheel rotatable about the axis of the rod and bearing against the case, and an internally threaded spring bearing cup that is prevented from rotating with respect to the case and that has a helical connection with the toothed wheel, said spring keeping the toothed wheel in abutment bearing against the case. A passage is provided between the actuators of two adjacent valves for introduction of a rotary adjustment tool for turning the toothed wheel.
In a particular embodiment, the adjustment tool includes a toothed sector meshing with the toothed wheel. In another embodiment, a toothed sector or gearwheel meshing with the toothed wheel is permanently mounted in the case. It is designed to receive the tool. For this purpose it can have a polygonal hole or socket of a shape corresponding to the shape of the end of the tool. In this embodiment, a gearwheel or toothed sector can be provided for each of the toothed wheels. The gearwheels or toothed sectors of two adjacent actuators can be offset relative to each other in the direction that is transverse to the direction in which the actuators are in alignment so as to reduce size.
The adjustment means can thus be placed axially in register with the single or top spring without increasing the axial size of the device. Adjustment can be performed when the actuator is in place.
In an advantageous embodiment, the tapped cup is prevented from rotating by a ring interposed between the spring and the cup and having projecting lugs into the case and sliding keying means with the cup.
The invention also provides a method of adjusting apparatus of the kind defined above. In the method:
(a) an adjustment tool is inserted in each passage and the corresponding toothed sector is meshed with a respective toothed wheel;
(b) the axial rest position of the rod of each actuator is measured;
(c) the toothed wheel of each actuator is turned until the rod has been moved into a determined position relative to the cylinder head or to the case of the corresponding actuator; and
(d) operations (b) and (c) are repeated after moving the tools across the passages so that their toothed sectors mesh with other toothed wheels, placed on the opposite sides of the passages.
In the first embodiment, the tool is moved laterally after being inserted to cause its toothed sector to mesh with one toothed wheel, and then with the other. In the second embodiment, it is engaged firstly in one toothed sector or gearwheel, and then in the other.
It is possible to adjust a plurality of toothed wheels simultaneously by using a plurality of tools that are inserted simultaneously and by using adjustment electronics that operates using time sharing. Nevertheless, it is generally preferable to perform adjustments successively with a single tool being inserted manually successively into the various passages, adjustment then taking place automatically with the help of electronics operating in a closed loop and put into operation under manual control.
In any event, the time required for adjusting the apparatus can be very short because adjustment can be automated by controlling the tool with the help of electronics that receives the output signal from a sensor for sensing the position of the armature, which sensor can be of the type described in French patent application No. 99/05203. It is possible to adjust half of the actuators simultaneously using electronics that operates with time sharing.
The above characteristics and others will appear more clearly on reading the following description of a particular embodiment given by way of example only.